Don't pigeonhole users to a specific theme based on age. Sure, use age to set an intelligent default theme, and provide a way for individual users to overide that and choose the theme they want.
Perhaps Mozilla could partner with DuckDuckGo and PureOS Librem and make a privacy-centric mobile smart phone with:
- PureFireDuck OS
- PureFireDuck search
- PureFireDuck voice & text
- PureFireDuck email
- PureFireDuck maps
- PureFireDuck app store (an app store unfriendly to spyware apps)?
Yes. Get whatever bike fits you. And I love my Tern [1] foldable bicycle. It folds into a bag which I can take anywhere in my car or on the bus or train and bike when I get there.